Benzanthrone carboxylic acids and process of preparing them



Patented Dec. 24, 1929 UNITED STATES PATENT OFFICE GEORG xRANzLEIn AND HEINRICH VOLLMANN, or: HOCHST-ON-THE-MAIN, GERMANY,

ASSIGNORS TO GENERAL ANILINE WORKS, me, on NEW YORK, N. Y., A CORPORA- TION OF DELAWARE BENZANTHRONTE CARBOXYLI C ACIDS AND PROCESS OF PREPARING THEM:

No Drawing, Application filed September 9, 1927, Serial 1T0. 218,573, and in Germany September 20, 1926.

Our present invention relates to benzanthrone carboxylic acids and process of preparing them.

Previous attempts to prepare benzanthrone 5 carboxylic acids by oxidation of alkyl lJOIlZilH thrones havefailed because thel'iz-nucleus of the benzanthrone was always ruptured by the oxidation treatment. Thus by oxidizing for instance Q-methylbenzanthrone there was obtained anthraquinone-l.2-dicarboxylic acid and by oxidizing Bz-alkylbenzanthrones there were obtained a-anthraquinonylketones (see our co-pending U. S. patent application Ser. No. 193,946 filed May 24, 1927).

thrones can be transformed with a good yield into benzanthrone 'carboxylic acids by a suitable alkaline oxidation i. e., by treatment with an oxidizing agent in the presence of alkali.

'20 The oxidation suitably may be carried out at temperatures between 100 C. andv 200 C. This is the case both with the Bz-methylbenzanthrones and with the benzanth'rones substituted in the anthra'quinone nucleus bya methyl group. In this manner there is obtained from Bz-l-methylbenzanthrone the already "known benzanthrone-Bz-l-earboxylic acid and from Z-methylbenzanthrone the hitherto unknown berizanthrone-Q-carboxylic acid:

and

our invention, but they are not intended to limit it thereto; the parts are parts by weight (1) 20 parts of Bz-l-methylbenzanthrone (obtainable according to our co-pending U. S.

Now wehave found that the methylbenz'an- I patent application Ser. No. 180,055 filed I March 31, 1927) are heated, while stirring, to about 150 C. together with 120 parts of nitrobenzene and 20 parts of powdered caustic pot- After the reaction has set in, the mixture is cooled to about 80 C. and filtered by suction. The residue contains the potassium salt of the carboxylic acid. It is dissolved in water, the adhering nitrobenzene is separated by means of steam, the aqueous brownish-yellow solution is filtered and the filtrate is pre- I ready known benzanthrone-Bz-l-carboxylic acid.

' (2) 80 parts of 2-methylbenzanthrone are heated to about 130 to 14:0 C. with 50 parts of caustic potash in 480 parts of nitro-benzene.

A reaction sets in with further self-heating 'and elimination of water which can be dlstilled off. After about hour the cooled re- OOH The followin examples serve to illustrate action-mass is filtered by suction and furthertreated as indicated in Example ("1) Recrystallized from nitrobenzene, the car-.

boxylic acid thus obtained forms yellow fiat needles melting at about 307 (1. to 308 C;

'tures.

, in a quite-similar manner. from Bz-2-methylbenzanthrone.

Weclaim: e 1. The process of preparing a benzanthrone carboxylic acid consisting in treating a methyl benzanthrone with an oxidizing agent in the presence of an alkali.

2. The process of preparing a benzanthrone carboxylic acid consisting in treating. 2-

methylbenzanthrone with an oxidizing agent in the presence of an alkali.

3. The process ofprparing a benzanthrone carboxylic acid consisting in treating a methylbenzanthrone with iiitrobenzene in the presence of caustic potash.

.4. The process of preparmg a benzanthrone carboxylic acid consisting in treating 2- methylbenzanthrone ,with nitrobenzene in the presence of caustic potash.

5. The process of prepari carboxylic acid consistingein treating amethyl benzanthrone with nitro nzeneinthe pres ence of. caustic potash at a temperature be tween 100 C. and200 C.

ng a benzanthrone 6. The process of preparing a benzanthrone carboxylic acid consisting in treating 2- methylbenzanthrone with nitrobenzene in the presence of caustic potash at a temperature between C. and 200 C.

7. The process of preparing benzanthrone-2-carboxylic acid consisting in treat ing 2-methylbenzanthrone with 'nitrobenzene in the presence of caustic otash at a temperature of 130 C. to 140 Y 8. The process of preparing benzanthrone -2 carboxyl'ic acid consisting in treating. 1 part of 2-methylbenzanthrone with 6 parts of nitrobenzene in the presence of about 'part of causticpotash at a temperature of 130C. to 140 C. a a

9. As a new product, benzanthrone-2- 7 carboxylic acid of the following formula:

crystallizing from nitrobenzene in flat yellow needles melting 'at 307 C. to 308? (3., dissolving in concentrated sulfuric acid to .a redsolution nearly without fluorescence, and

\in sodium carbonate-or other alkali solution to a yelhiwsolution which shows when diluted with water a stro g'g nfluorescence.

GEORG KRZiNZLEH T. HEINRICH VOLLMANN.

In testimony whereof, we our signa- 

